目录

一、定义 

二、示例：

三、生成：

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一、定义 

        使用checked关键字处理溢出。

        在进行数学运算时，由于变量类型不同，数值的值域也有所不同。如果变量中的数值超出了变量的值域，则会出现溢出情况，出现溢出时变量中的数值将不准确。怎样有效地防止溢出呢?下面结合实例演示怎样使用checked关键字检查是否出现溢出。

        例如，数值类型为byte，byte类型的值域为0～255，所以如果byte类型变量的值高于255或者小于0都会出现溢出。

二、示例：

// 使用checked关键字判断是否有溢出
namespace _022
{
    public partial class Form1 : Form
    {
        private Label? label1;
        private Label? label2;
        private Button? button1;
        private TextBox? textBox1;
        private TextBox? textBox2;
        private TextBox? textBox3;
        
        public Form1()
        {
            InitializeComponent();
            Load += Form1_Load;
        }
        private void Form1_Load(object? sender, EventArgs e)
        {
            // 
            // label1
            // 
            label1 = new Label
            {
                AutoSize = true,
                Location = new Point(65, 18),
                Name = "label1",
                Size = new Size(43, 17),
                TabIndex = 0,
                Text = " + "
            };
            // 
            // label2
            // 
            label2 = new Label
            {
                AutoSize = true,
                Location = new Point(150, 18),
                Name = "label2",
                Size = new Size(43, 17),
                TabIndex = 7,
                Text = " = "
            };
            // 
            // button1
            // 
            button1 = new Button
            {
                Location = new Point(247, 15),
                Name = "button1",
                Size = new Size(75, 23),
                TabIndex = 3,
                Text = "计算",
                UseVisualStyleBackColor = true
            };
            button1.Click += Button1_Click;
            // 
            // textBox1
            // 
            textBox1 = new TextBox
            {
                Location = new Point(12, 15),
                Name = "textBox1",
                Size = new Size(50, 23),
                TabIndex = 4,
                Text = "100"
            };
            // 
            // textBox2
            // 
            textBox2 = new TextBox
            {
                Location = new Point(99, 15),
                Name = "textBox2",
                Size = new Size(50, 23),
                TabIndex = 5,
                Text = "200"
            };
            // 
            // textBox3
            // 
            textBox3 = new TextBox
            {
                Location = new Point(182, 15),
                Name = "textBox3",
                Size = new Size(50, 23),
                TabIndex = 6
            };
            // 
            // Form1
            // 
            AutoScaleDimensions = new SizeF(7F, 17F);
            AutoScaleMode = AutoScaleMode.Font;
            ClientSize = new Size(334, 91);
            Controls.Add(label2);
            Controls.Add(textBox3);
            Controls.Add(textBox2);
            Controls.Add(textBox1);
            Controls.Add(button1);
            Controls.Add(label1);
            Name = "Form1";
            StartPosition = FormStartPosition.CenterScreen;
            Text = "使用checked关键字处理溢出";           
        }

        private void Button1_Click(object? sender, EventArgs e)
        {
            if (byte.TryParse(                             //对两个byte类型变量赋值
                textBox1!.Text, out byte Add_One)
                && byte.TryParse(textBox2!.Text, out byte Add_Two))
            {
                try
                {
                    checked { Add_One += Add_Two; }        //使用checke关键字判断是否有溢出
                    textBox3!.Text = Add_One.ToString();   //输出相加后的结果
                }
                catch (OverflowException ex)
                {
                    MessageBox.Show(ex.Message, "出错！"); //输出异常信息
                }
            }
            else
            {
                MessageBox.Show("请输入255以内的数字!");    //输出错误信息
            }
        }
    }
}

三、生成：